How Old Are the Three Sons?

I thought this was a good one. All my friends who I've shown it to (except for one) haven't been able to solve it.

Many years from now, two men are sitting in the county park. The
following is part of their discussion:

Man 1: Yes, I'm married and have three fine sons.
Man 2: That's wonderful! How old are they?
MaN 1: Well, The product of their ages is equal to 36.
Man 2: Hmm. That doesn't tell me enough. Give me another clue.
Man 1: Ok, the sum of their ages is the number on that building
across the street.
Man 2: A ha! I've almost got the answer, but I still need another
clue.
Man 1: Very well. The oldest one has red hair.
Man 2: I've got it!

answer in white font 2, 2, and 9 ... there are 6 possible age combinations, only two give ambiguous sums of ages (2, 2, and 9; 1, 6, and 6) and it must be one of these or else the house number would have solved the problem in step 2; only 2, 2, and 9 gives a single 'oldest' child as the alternative (1, 6 and 6 has tiwn boys as oldest